adccommunitymod (AutomationDirect) asked a question.
Created Date: December 05,2006
Created By: krak
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i am looking for a way to control the speed of a single phase motor that is 1/20 hp. i want to be able to have a plc control when the motor is on and how fast it will go. this will be for a conveyor system that will need to turn on and off a lot. absolute speed control is not needed, neither is feed back. i 've been looking at servos, steppers, and 3 phase motors. but the cost is higher then value of the product. is there a off the shelf solution to control a motor with about 60 rpm output ( using a gear reducer ) that can be controlled via plc either analog or comm's. i will need up to three of these setups per plc. any tips?
Created Date: December 05,2006
Created by: bcarlton
I don't have a specific answer but I suggest you look into how room fans are speed controlled. I believe they are windings controlled by switched resistor/capacitor networks. Since you don't need precise speed control, that may be the answer. Better yet, buy a multi speed fan and rip it apart.
Created Date: December 05,2006
Created by: KPrice
krak, I would suggest a DC motor and DC motor drive. Grainger offers a large selection. They offer DC drives that accept analog signals, VDC and ma, for speed control. You can use 115VAC or 230VAC single-phase power input. They also have gear motors with various ratios. Room fan speed controls chop the AC sine wave, twice per cycle. Hope this helps.
Created Date: December 05,2006
Created by: krak
i took a fan apart, and found that it powers 1,2,or 3 windings to control speed. i was looking into grainger for the dc motors and drives. i was just hoping for a simple cheaper option. do you know if i would have isolate the analog signal between a drive like grainger item 5JJ57 and F0-4AD2DA-1?
Created Date: December 06,2006
Created by: KPrice
krak, The 5JJ57 does not have an analog follower circuit. However, Dart does offer drives with 0-10VDC follower circuits. They also offer option boards, field or factory installed, that accept 4-20ma. But you would need a signal conditioner, FC-11, because the F0-4AD2DA-1 can only drive 300 ohm max and the Dart 4-20ma option is rated at 500 ohm. Sorry, I guess this DC motor idea is too expensive. Could you get by with the PLC simply switching the windings of a 3-speed motor for low, mid, or high?
Created Date: December 06,2006
Created by: allukes
KB Electronics sells fractional HP Drives in a chassis version with optional Analog option boards also. http://www.kbelectronics.com
If you can deal with several speed ranges, there is also a trick that you can do with a standard speed pot and a series of resistors and relays. Relays are pretty cheap, so you can short out resistors to change the speed pot divider on a standard drive.
Created Date: December 07,2006
Created by: krak
fine control of the motor speed is not needed, however i would need a little better control then a three speed setting would winding system would offer. i am looking to have the motor run between 30 and 60 rpm, and have about 100 in-lbs (after the gear reducer). i was looking at the cheap product in grainger. i was thinking of simply tieing the pot into the analog output of a card. i haven't done that before. in theory i think it would work, but i would rather ask first, then to pay and break who knows what. am also open to the idea of using a network to control the drive.
Created Date: December 07,2006
Created by: allukes
You might want to talk to Dart and find out what the potentiometer circuit looks like before hooking anything to it. There would be a good chance it would pop your analog card if not more.
Created Date: December 07,2006
Created by: krak
that's what i was thinking. my mext question is about the voltage follower. i 've never heard this term before. is it another way of controlling the speed output of the drive? if this is so then i think can use this type of controller. it still keeps the price per unit below $1000 which is easy to fit into my budget.
Created Date: December 07,2006
Created by: allukes
Take a look at http://www.kbelectronics.com/manuals/kbic.pdf
Here is an excerpt from the above manual.
C. Voltage Following " All models can be controlled with an isolated analog reference voltage (0-7 VDC) in lieu of the main speed potentiometer. The voltage is connected to P2 (+) and F-. The control output voltage will linearly follow the input voltage.
The source impedance of the input should be 10K ohms or less. The Min and Max trimpots are rendered inoperative in the
voltage following mode. Use auxiliary trimpots for scaling and to limit the control range. If the input signal is not isolated, or is a current signal (4 - 20 mA), the KBSI-240D or SI-5 Barrier Terminal Board Signal Isolator must be used. It will allow direct connection to process controllers and microprocessors.
The standard KBIC fractional HP drives are about $80 each
Created Date: December 07,2006
Created by: milldrone
Krak,
I just ran this combination on my workbench. I used a GS2 controlled by modbus and a 2z800 motor on one phase of the GS2. I limited the voltage at 60 hz to 120V. The GS2 I used is a 230V single phase input 3 phase out 3HP unit, It didn't trip on the light load from the motor. The universal motor did change speeds in response to the voltage- speed input but this type of motor is notorius for bad speed control under changing load. Maybee some GS1's would work and by using modbus you could save on the analog module. I didn't have a shaded pole motor to try or I would have tried one.